1. Field of the Invention
The present invention relates to a liquid-transferring pump for medical use. More specifically, the present invention relates to a turbo blood pump for transferring blood by providing blood with thrust by the rotation of an impeller.
2. Description of the Related Art
Conventionally, in extracorporeal circulation in an operation using an artificial heart lung apparatus, etc., a roller blood pump has been used mostly. Recently, however, centrifugal blood pumps increasingly have been used. This is because, as compared with roller blood pumps, the centrifugal blood pumps (turbo blood pumps) have various advantages, for example, little damage to blood, etc. Furthermore, as compared with a driving portion of a conventional large size roller blood pump, the centrifugal blood pump may have a smaller driving portion. Therefore, the centrifugal blood can be disposed and carried easily.
However, when the centrifugal pumps are used in a clinical application, there have been the following problems to be solved. Firstly, the centrifugal blood pumps have a problem as to the amount of blood to be filled. In centrifugal blood pumps, in order to reduce hemolysis, driving at a low rotational speed is desired. However, if the rotational speed were reduced, it was necessary to increase the size of the pump in order to obtain the same discharging ability (liquid transferring amount). If the size of the blood pump were increased, the amount of blood to be filled was increased. As a result, the amount of blood for extracorporeal circulation is increased, thus burdening a patient more.
On the contrary, in order to obtain a sufficient amount of blood with a smaller-size pump, the impeller has to be rotated at high speed. In such a case, it is not possible to realize the reduction of hemolysis (damage to blood), etc.
Furthermore, if a centrifugal pump, in which the standard such as rotational speed, amount of liquid to be transferred, amount of liquid to be filled, etc. is set for an adult patient, is used for a child patient or a patient who cannot tolerate a large amount of blood circulation, the pump has to be used at the lower rotational speed, and it is difficult to adjust and maintain the amount of liquid to be transferred.
Furthermore, not a few of conventional centrifugal pumps have a structure in which blood tends to stagnate in the central portion of the lower surface of the impeller. When such a centrifugal pump is used, there arise some problems in that thrombus tends to be formed, and it is difficult to use such a pump for a long-time extracorporeal circulation, etc.
With the foregoing in mind, it is an object of the present invention to provide a blood pump avoiding the above-mentioned problems. That is, the first object of the present invention is to provide a turbo blood pump having a small size (blood to be filled is small) and capable of adjusting and maintaining a slight amount of flow. The second object of the present invention is to provide a turbo blood pump with little hemolysis even if it is used in a practically high rotational speed necessary to achieve a predetermined discharging ability.
In order to achieve the above-mentioned object, the turbo blood pump of the present invention includes a housing having an inlet port and an outlet port; and an impeller disposed rotatably in the housing. The impeller includes at least a rotation shaft, plural vanes and an annular connection portion. The plural vanes are connected to the annular connection portion in a part at the side of the outlet port, and some or all of the plural vanes are connected to the rotation shaft by a supporting member in a part at the side of the inlet port, and a vane inlet side line k of the plural vanes, which connects an inlet side upper end and an inlet side lower end of the plural vanes, is in the skew position with respect to the rotation shaft and a vane outlet side line l of the plural vanes, which connects an outlet side upper end and an outlet side lower end of the plural vanes.
Furthermore, it is preferable that the above-mentioned turbo blood pump of the present invention has the following embodiments. According to the first embodiment, the vane outlet side line l is in parallel with the rotation shaft. According to the second embodiment, an angle made by the vane inlet side line k and an axis intersecting the vane inlet side line k and parallel to the rotation shaft is set to be larger than an angle made by the vane outlet side line l and an axis intersecting the vane outlet side line l and parallel to the rotation shaft.
According to the third embodiment, an angle made by a vane upper surface line m that connects the inlet side upper end and the outlet side upper end, and an axis intersecting the vane upper surface line m and parallel to the rotation shaft is set to be smaller than an angle made by a vane lower surface line n that connects the inlet side lower end and the outlet side lower end, and an axis intersecting the vane lower surface line n and parallel to the rotation shaft.
According to the fourth embodiment, assuming a first circle passing the inlet side upper end, which is concentric with the outer periphery of the impeller, a tangent line p of the first circle, which passes an intersection point of the vane upper surface line m of one vane and the first circle, a second circle passing the outlet side lower end, which is concentric with the outer periphery of the impeller, and a tangent line q of the second circle, which passes an intersection point between the vane lower surface line n of the one vane and the second circle; an angle xcex8 made by the tangent line p and the vane upper surface line m of the one vane is smaller than an angle xcex5 made by the tangent line q and the vane lower surface line n of the one vane.
According to the fifth embodiment, the profile of the vane presents a shape of a curved surface that smoothly connects the vane inlet side line k and the vane outlet side line l, the shape of the curved surface is a shape obtained by shifting the vane inlet side line k that is in the skew position with respect to the rotation shaft along the radius direction toward the outer periphery of the impeller while allowing it to convolute until it becomes in parallel with the rotation shaft.
According to the sixth embodiment, the plural vanes are made of a first vane and a second vane, which have different areas. In this embodiment, the first vane and the second vane are disposed so that they are in a position of rotational symmetry with respect to the rotation shaft and the total number of the plural vanes is in the range from 4 to 8.
According to the seventh embodiment, a driving shaft having driving magnets at the side of the housing is provided outside the housing and the annular connection portion is housed in a pump chamber in the housing has driven magnets to be attracted by the driving magnets via the inner wall of the housing.
By using the turbo blood pump of the present invention, various problems mentioned above can be solved. Firstly, even in a liquid transferring pump with a small size (amount of blood to be filled is small), a large flow amount of liquid can be transferred. And by increasing the rotational speed, it is easy to adjust and maintain the amount of liquid to be transferred. Second, even if the liquid transferring pump operates at practically high rotational speed, the hemolysis degree is small, thus reducing the damage to the body. As a result, it is possible to be applied to a long time extracorporeal circulation.